Somewhere around the third triple-digit day of a Utah heat wave, the same doubt creeps into every house: is the AC failing, or is it just this hot? The house won’t get below 79, the unit never seems to shut off, and the utility bill is bracing for impact.
Recent summers along the Wasatch Front keep landing among the hottest on record, so this question isn’t going away. Here’s the honest guide to what your air conditioner is actually built to do in extreme heat, how to tell a healthy system from a struggling one, and why the hottest years are exactly when maintenance stops being optional.
Your AC was sized for a hot day — not the hottest day ever
Residential cooling systems aren’t sized for the worst afternoon of the decade. They’re sized around a design temperature — a statistically typical hot day for the area, which for the Salt Lake Valley sits in the mid-90s. On a 95° afternoon, a correctly sized, healthy system holds the house comfortable without heroics.
Push past that — 100°, 103°, 106° — and the system is being asked to do more than it was sized for. What that looks like from the couch:
- It runs continuously. Normal, and actually correct. Long steady runs in extreme heat are how the system is supposed to behave.
- It holds roughly a 20-degree gap below outside, not a fixed indoor number. At 105° out, an indoor 82° can be a machine doing everything right at full capacity — not a breakdown.
- It loses ground in late afternoon and catches up in the evening. Also normal on the worst days.
Knowing this saves two kinds of grief: panic-calling for a repair the system doesn’t need, and — the opposite mistake — assuming “it’s just the heat” when something is genuinely wrong.
The 2-minute check that tells you which one you have
You can test a cooling system’s basic health with a kitchen thermometer:
- Hold it in the airflow at a return grille (where air gets pulled in) and note the temperature.
- Hold it in the airflow at a supply vent (where cold air comes out) and note that too.
- A healthy system blows air roughly 15–20 degrees colder than what it pulls in — even on a brutal day.
Split in that range and the unit running constantly? Your AC is fine; the weather is the problem. Split of 10 degrees or less, or any of the following, and it’s time to get it looked at:
- Ice on the copper lines or the indoor coil
- Rapid on-off cycling instead of long runs
- Air that’s moving but barely cool
- The outdoor unit tripping the breaker
- New grinding, screeching, or buzzing
Two free things worth checking before you call anyone: a clean filter, and an outdoor unit that’s clear of cottonwood fluff, grass clippings, and leaned-up patio gear. A choked filter or a blanketed coil can single-handedly fake most of the symptoms above.
The part nobody sees: heat waves age your AC
Here’s what the record-hot summers actually cost, beyond the power bill. Wear on an air conditioner tracks hours of runtime under load. More 100-degree days means more hours at maximum effort — there’s no way around that part.
What you can control is how much strain those hours carry. A clean, correctly charged, well-adjusted system moves the most heat per hour of effort. A struggling one — dirty coil, tired filter, low refrigerant charge — delivers less cooling per hour, so it hits its capacity ceiling sooner, falls behind on days a healthy unit would handle, and runs even longer trying to catch up. Strain compounding strain, all summer. That’s the quiet mechanism by which neglected systems come out of a heat wave years older than their calendar age.
This is why our answer to “it’s working, do I still need a tune-up?” is an honest yes. A tune-up isn’t for broken systems — it’s what keeps a working system from becoming one. It restores the efficiency the summer scraped away, which lowers runtime, bills, and wear all at once. And in one narrow sense it’s close to required: most manufacturer warranties expect documented annual maintenance, so the service records protect your coverage too.
Ours is a $120 full working tune-up — the genuine checklist, not an inspect-and-quote visit, with no expiration date. An end-of-season visit catches whatever this summer damaged before the unit sits all winter, and fall is also the moment to get the furnace checked in the same season.
Where we come in
If the 2-minute check worries you, the $69 diagnostic gets a professional set of eyes and gauges on the system — waived if we do the repair, credited toward a new unit if the honest answer is that yours is done. Most of the time it isn’t: the majority of “my AC can’t keep up” calls end in a modest repair or an overdue cleaning, not new equipment. And on the occasions it really is the end, replacement happens in one day, with market pricing you can sanity-check against our cost guide and our free 5-year labor warranty behind the work.
Want a professional read on how your system weathered the summer? Call or text (801) 678-5748 — Monday through Friday, 8 AM to 8 PM, English or Spanish — or book online. Honest opinion first; everything else is your call.